Comments

I've got 55k miles on my Tahoe and indicator lights for the 4 wheel drive will come off sometimes when I start the car. Other times it will already be set in 4 wheel low. Obviously I need to get it serviced. I'm just surprised that happening with only 55k. Something I should cautious about when getting it fixed?

The fan switch on my 1999 Tahoe seems to work only when Hi is selected, although there are occassions when dropping down to Med-Hi that fan still runs and sounds as though there is no change in fan speed. There are also times the fan does not run when Hi is selected as well......

I have a 2004 Suburban. When I start my suburban, it will be in 4L or 4H or the red light N, or no indication at all. My Service 4WD light will come on after a while. Sometimes it works fine. I have read lots of fixes, like a ground wire no being connected, the switch needs to be replaced, the sending unit is bad, and finally, a computer chip is messed up. A friend of mine had a computer chip replaced, and that fixed his....of course, his truck was still under warranty... mine is not. If anyone has had any luck with a certain type of fix for this, please let me know so I can go to the dealer with some knowledge, so help save me a little dough. Thanks.

I own a 2003 Chevy suburban and have the same problem with the 4wd and I found out that in times you need to get it working you can pull the fuse ("TREC" all wheel drive module) from under the hood and wait 15 seconds and install it again. This is the fuse for the all wheel drive module. Do this when the truck is running and it should activate the module to get everything working again. Living in Wis. you need 4wd to get around in the snow. I was told that the module does not sense the power so it does not turn on. now it been working fine for 3 months now and it did not cost me anything. This not a fix all solution but it worked for me. right now

i have 2001 suburban the check 4wd light comes on sometimes and stays on until you turn car off. might not come for a week or two then does same thing again. there are no service codes in computer. any ideas.

I had a problem where not only would my "SERVICE 4WD" indicator light come on, but it would actually shift itself into 4WD when I started it up. I replaced my dash 4WD switch w/ a new one. It cost about $55 w/ shipping. Since I have put it in, the "SERVICE 4WD" indicator light, has not come on. But, I have noticed as it starts to get warmer outside, I am still having the problem where I my Suburban will show the RED "N" light on my 4WD buttons. So I may have to actually get the Chevy dealership to look at it..... and then take out a loan to pay for it!!

This is a fairly common problem. Chevrolet has determined the Transfer Case Control Module sometimes does not get the "wake up call" it expects upon start up.

There is a TSB issued, 02-04-21-006E. Available via subscription on All Data among other places. The TSB discusses removing the fuse as described in this forum. Failing that, the TCCM requires replacement. There is a reprogramming routine that must be performed on the new TCCM, have not done this myself but expect it is not all that difficult.

One day while attempting to shift into 4wd high from 2wd, all lights went out on the 2wd-4wd-4wd low swith and the "Service 4wd" light came on. I had a '99 Tahoe that did this once and replcing the fuse worked. I did the same thing but it didn't help. I unhooked the battery to attempt to reset the 4wd and the "Service 4wd" light is no longer on but the problem still exists. It appears to be in 2wd now but the snow is coming! What's the deal?

To several of you on the forum, I noticed your concerns were over a year ago - so what happened? Did you have to replace the Transfer Case Control Module (TCCM)? I'm experiencing all of those systems you all have gone thru - the "check 4WD " message, no codes announcing anything's wrong, the off-on lite effect with the shift selection buttons etc. I went on Chevrolet Just Answer.com, and got a definitive response to change the TCCM. Even got the repair manual guidance and instructions on how to do it - but havent done it yet. No where in the simple bolt out bolt in , unplug replug process does it describe a "reprogramming". Hope this info is of some value. Welcome any responses. My Tahoe is a 03 Tahoe LT.Chek

I felt pretty dumb when I realized there was an additional fuse under the hood of my 2001 Suburban (ATC) for the automatic transfer case. I had only checked the fuse inside the cab when the 4WD went out and it wasn't until I read another post that I realized there was another one. The ATC fuse was blown when I checked it. Even though the car wasn't on I heard the transfer case shift when I replaced the fuse. It has been fine since. Time to buy a couple more fuses! :shades:

Don't feel too bad Bryons. I too am going through the same thing on our 1997 Tahoe. Replaced Universals earlier this week. Then 4WD would not work. Got it to go into 4WD. Now it is tuck there. Checked all the connections and the dash fuse. Was ready to take it to the dealer until I found this forum. Tomorrow will be checking for the ATC fuse! Now if someone could tell me were it is located under the hood it would be appreciated! Thank you.

The '99 and older are different but the one for my 2001 is located in a black plastic box under the hood above the left front wheel. I cross-referenced the "ATC" with the owners manual and found it for the automatic transfer case. It only made sense to check it, and, it had blown! Check your owners manual for exact location and what each fuse is for. Good luck! I hope you don't have to pay the dealer. $$$

My 1999 Tahoe (odo reading 137,400 miles) won't go into 4 wheel drive. A couple of days ago the "Check 4WD" light came on for a while and then went off. I planned, but haven't done so yet, to get all the fluid levels checked this weekend. But now I see the red "Neutral" light is lit and I can't engage 4 wheel drive. I f there is a low fluid level sensor, can low transfer case or front diff lube cause this?Also, I want to check the ATC fuse per the above messages, but my owner's manual doesn't show where it is.Can any one please advise? Thanks,

So I have to pose a question to all those out there in computer land who are smarter than me or happen to be mechanics or have had this issue before.

I recently purchased a 1998 Tahoe with the right side of dash push button 4x4 with the auto 4x4 and the previous owner stated he was driving it in 4Hi and when he went to go into 2Hi it wouldn't shift and went into neutral.

When I bought it the Transfer Case Shift Motor was removed I was able to shift it manually into 4Hi, 4Lo and neutral but couldn't seem to find 2Hi. I replaced the Shift Motor and checked the fuses and it still wouldn't shift. I did get the lights on the dash to blink for a while and then they seemed to go out completely.

I took it to Chevy who put the motor back in (cuz I had to remove it to manually shift into 2wd) and stated it wasn't working because the Transfer Case Module under the dash was bad. $350 later plus labor they stated it tried to shift a few times and then burned out the Transfer Case Shift Motor $225 plus labor. After all this and not seeming to get it into 2wd they want me to replace the whole T-Case $750 used.

Any advise before I replace the T-case or does this sound wrong to anybody else?

read some of the feed back.My problem is the indicator lt stays on in all wh, pressing the 2w 4w 4wlow dosnt shift.Replaced the modual in the dash still nothing , :mad: only 250 $not like azfireman.Will try the fuse removal senario.Any other ideas?

Thanks for all the suggestions, but I can't find the automatic transfer case (ATC) fuse. I checked my owner's manual and looked at both the instrument panel fuseblock (on the left side) and the fuse panel under the hood on the left hand front fenderwell. Is there another fuse panel location not shown in my manual? I am going to try the battery disconnect method to see if re-booting the ECU and Trans Control Unit will help.

I would appreciate hearing from anyone who knows where the ATC fuse is located on a 1999 Tahoe. Thanks for your help so far.

I realize your Tahoe is a 2001 and mine is a 1999, but where did you find the ATC fuse? I looked at my manual and opened the fusebox on the left front fenderwell, but didn't see the ATC fuse. The fusebox I opened has many fuses and relays in it. Is this the correct panel or is there another fusebox you're talking about, or does the ATC fuse have a different name or designation??

A big thanks to all who made suggestions. My 1999 Tahoe now has a correctly functioning 4WD system. If you recall, NIKT (that&#146;s me) said that the unit was stuck in 2HI and would not engage any other mode. There were various suggestions, but here&#146;s what worked for me:

1.- Find ATC fuse. This took longer than everything else because I kept looking for an &#147;ATC&#148; fuse. At least on my &#146;99 Tahoe, there&#146;s no fuse so marked. My manual did list a fuse in the small fuse panel on the left side of the instrument panel, but not in the panel over the left front wheel. It&#146;s a 20Amp fuse in the No. 2 position, and is identified as &#147;Transfer Case.&#148; It was blown.

2. &#150; I pulled the T-case fuse (#2) and the Accessory Light fuse (#3) and left the car sit for about 5 minutes with the ignition switch off.

3 &#150; I replaced the 20 Amp fuse with a 25 Amp fuse, because some people suggested that cold weather can result in a higher current draw in the 2WD-4WD shift motor. I put back the 10 Amp Accessory Light fuse which was OK.

4. &#150; As some suggested, I then switched the ignition On and Off 5 times to clear any trouble codes stored in the Trans Control Module.

5. &#150; I fired up the engine and watched as the red &#147;Neutral&#148; light on the control button panel blinked off. My Tahoe had been stuck in 2HI, but then the 4HI button lit showing that mode was now engaged. I pushed the 2HI button and the transfer case shifted OK. Out on the street I engaged all the Transfer Case modes and everything seemed to work OK.

Again, a big thanks to you all, and I hope what I did works for you too.

I'd put a 20Amp fuse back in. If you really do have some sort of problem (which will trip now the 25Amp fuse), you may burn some wiring (or a wiring block or connector) which would be very costly to repair.

You can also keep another spare if it does blow later. If it does, you'll know exactly what are where to replace it.

checked the 20amp atc fuse that was to easy.subscibe to all data not all you want to know,. to seek more diagnostics.The selector seems to have power and replaced the modual.Has anybody gone further and replaced the tccm thier on ebay 165.00 pluged a scaner in ,no codes?

Thanks for your thoughts. You make good sense and I will change the fuse back to a 20 Amp unit this morning and keep some spares handy, Also, I will operate the 4WD drive selection every other day or so to keep the shafts or other components moving freely.

Also, is there another recommended lube oil for the transfer case? Some forums talk about a "blue" fluid for better lubricity, or is that to improve the Auto 4WD?

You know, I have never used the Automatic 4WD feature. I bought my Tahoe used (50,000 miles) about 9 years ago. I tried using the Auto 4WD in the snow, but I didn't like what I thought was a harsh engagement and avoided ever using it. When accelerating on snow or wet pavement, I engage 4HI to get up to speed and then engage 2HI. In winter here in suburban Chicago, when we get blowing and drifting snow, I engage 4HI and it seems to get me through just fine. I then shift back to 2HI when I'm back on dry ground. I'm coming up on 140,000 miles and I like my Tahoe just fine. The only repairs of consequence (how do you spell Co$t?) have been replacement of one fuel injector and about 2 years later, the in-tank fuel pump.

I can't speak with the authority of a mechanic, but only from my perspective as a Tahoe owner. You may already know this, but don't engage 4WD on dry ground. If I correctly understand the way the 4WD system functions, engaging the front axle also causes the front axle to become a locked axle. That's necessary to prevent all the drive torque going to one wheel on very slippery ground, leaving you with very little or no traction. This means (to me) that one should avoid sharp turns of the front wheels while in 4WD unless you are on very slippery (snowy, icy) ground. I recall once forgetting to disengage 4WD and I could feel a terrific binding when I made sharp turns on dry ground.

Did you read my previous entry? I bought my Tahoe used, and didn't like the way Auto 4WD engaged and never used again. Maybe a Tahoe technician could advise on lube oil specs for the transfer case. I hope this helps.

I have the same problem on a 2003 Chev Blazer, with nearly identical symptoms.

If you believe the push button 4WD selector, all is fine. It switches in and out of 2 or 4WD no problem. However, based on recent driving I don't think it's actually engaged. If I actually get some decent slippage (ie, icy accelerating), it will grind from the front end like crazy. Sounds similar to grinding gears on a manual transmission (it's an auto, for reference). Only happens on slippage in 4WD.

Took it into the dealer, they've replaced a seal which they say went bad and let oil into my vacuum lines which then took out a servo and actuator. Still grinds, so they're thinking it's actually taken chunks off the gear and sleeve for the 4WD. $800 so far into it, gonna be about $800 more for the gear and sleeve. Does this sound right for symptoms/diagnosis? I'm not much of a mechanic and REALLY get lost on tranny/transfer case type stuff.

I took it to a shop, they said bad transfer case, they can put in a new one for $2,000

i found a use one at the junk yard for $300. my friend and I are going to put it in and see what we get. They are supposed to be heavy so a little bit tricky to do in the driveway. I'll let you know how it turns out.